Can Protein Shakes Make You Nauseous? (Yes, Here’s Why)

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There have been multiple reports of people feeling nauseous after drinking protein shakes. 

This Reddit user said they felt like “puking a couple of hours” after drinking whey protein. Another Reddit user said they used a vegetarian protein powder, and even 1 scoop made them feel nauseated to the point where they actually threw up.    

So, can protein shakes make you nauseous?  Yes, protein shakes can make you nauseous. A low-quality protein, or one that contains inulin fiber or artificial sweeteners can cause nausea. Drinking too much at once, drinking it too fast or too close to your workout can be other factors. Nausea might also indicate a lactose or protein allergy more broadly. 

As the manager of a supplement store for the past ten years, one of the main parts of my job involves helping customers find a protein powder that they both enjoy and tolerate to help them achieve their results. 

In this article, I’ll dive into: 

  • 7 reasons why your protein shake might be making you nauseous (and how to fix it!)
  • Steps for choosing whey protein that won’t make you nauseous
  • What to do if you still get sick after implementing these tips
  • My TOP protein recommendation for people who get nauseous

What Are The Signs That Your Protein Shake Is Making You Nauseous? 

There are a few possible reactions you might have after taking protein powder that indicate it’s not the right product for you. 

If you experience gas, bloating, diarrhea, cramping, or general nausea after taking a protein powder, it’s time to manipulate how you are taking your protein, or consider switching powders altogether.

If you want to make sure that it’s your protein shake that is making you nauseous, and not other factors throughout your day, have 1 scoop of your protein powder mixed with 6-8 ounces of water first thing in the morning. Drink it slowly over 5 to 10 minutes rather than all at once.  

If you experience negative gastrointestinal symptoms like nausea, bloating, or gas after having only the protein shake with water, then it’s likely the protein powder itself that is the problem. 

If you don’t experience nausea after drinking your protein powder away from your workout, but you do experience nausea when taking your protein powder after the workout, then it’s probably the way you’re drinking it (e.g. drinking it too close to your workout, drinking it too quickly) and not the actual protein powder. 

Note: If you get diarrhea as a side effect, go to my other article on Protein Shakes & Diarrea as there are some specific causes and fixes that go above and beyond simply feeling nauseous.  

Struggling with food intolerances? Let a FeastGood nutrition coach help you.

7 Reasons Whey Protein Shakes Can Make You Nauseous 

7 reasons whey protein shakes can make you nauseous 

The 7 reasons that whey protein can make you nauseous are:

  • You’re using a low quality protein
  • Your whey protein contains inulin fiber
  • Your whey protein contains artificial sweetener
  • You’re taking too much protein at once
  • You’re drinking your protein shake too quickly
  • You’re drinking your protein shake too close to your workout
  • You have a lactose intolerance you didn’t know about

1. You’re Using a Low Quality Protein

As consumers are becoming more educated, they are demanding more from supplement companies which have been largely a good thing, requiring supplement companies to step up and produce higher quality products. 

Unfortunately for protein powders, however, since they are considered a dietary supplement, they are not regulated by the Food and Drug Administration (FDA). This results in a wide disparity in the quality of protein supplements. 

A lesser quality protein will have more additives, fillers, or cheaper sources of whey that are higher in lactose and more likely to cause stomach upset. 

Here’s one of my top tricks for quickly identifying higher-quality protein powders: 

Take the total grams of protein per scoop, divided by the total grams of the scoop size then multiply by 100.

For instance, with this product (Allmax Isoflex), it offers 27g of protein per 30g scoop. 27 divided by 30 = 0.9 multiplied by 100 is 90. What this tells you is that the product is 90% protein per scoop.

Compare that to this whey protein from Six Star Nutrition:

Six Star Nutrition

The scoop size is 47g, and it offers 30g of protein. 30 divided by 47 = 0.64 x 100 = 64. That means that for each scoop of this product that you take, only 64% of that scoop is protein. That leaves 36% of “other stuff” in your protein powder like sugar and additives.

Ideally, you want this number to be as close to 100 as possible. A protein powder with a protein percentage higher than 85% is an excellent quality product. One that falls between 75% and 85% is a good quality product. 

If you are shopping specifically for protein powder and not a meal replacement, then I would stay away from any powder with a ratio that falls below 75%.

How To Fix

The first step in assessing your protein supplement quality is to determine the protein percentage. If your product falls below 75%, then switch to a protein powder that has a higher percentage.

If your protein powder does fall in the good to excellent categories, but still causes nausea or upset, check the list of non-medicinal ingredients. 

There should be very few ingredients here, limited mostly to the protein itself, and natural or artificial sources of flavor or color including cocoa, vanilla, stevia, sucralose, and beetroot powder.

2. Your Whey Protein Contains Inulin Fiber

Inulin is a type of soluble fiber found in plants that are sometimes added to food products to alter the texture or replace sugars and fats

While inulin fiber does generally offer a host of gut health benefits because it is a prebiotic fiber, which means it feeds the good bacteria in our gut, it can come with some negative side effects. 

The most common negative side effects of inulin fiber intake include gas, bloating, abdominal discomfort, and diarrhea or loose stool. 

How To Fix

Choose a protein powder that does not contain inulin fiber. You can find this by checking the non-medicinal ingredients and looking for the following items: inulin, oligofructose, chicory root, or chicory root extract.

3. Your Whey Protein Contains Artificial Sweetener

The three most common sweeteners you will find in protein powders include acesulfame potassium, sucralose, and stevia

Acesulfame potassium (also called Ace-K) is a calorie-free sweetener approved by the FDA with more than 90 studies backing its safety. A review of the literature finds no mention of any gastrointestinal upset with Ace-K, so it’s unlikely that this ingredient is problematic. 

Sucralose is a non-calorie sweetener derived from actual sugar that is 600 times sweeter than real sugar. Sucralose has been proven safe in more than 110 studies.

Stevia is widely regarded as a more natural alternative, as it originates from the leaves of the stevia plant. It is 200 to 300 times sweeter than table sugar. 

In my research, I found a lot of anecdotal evidence about artificial sweeteners causing nausea or bloating, and I found a few incidences of doctors allegedly making these same claims, but I couldn’t find any peer-reviewed articles that demonstrated the same thing. 

The closest I came to a verifiable source was WebMD indicating that side effects of stevia include bloating and nausea. I did, however, find a lot correlating artificial sweeteners with migraines.

Sugar alcohols, on the other hand, like erythritol, maltitol, and xylitol, are known to be more likely to cause symptoms of nausea and GI upset. 

This all being said, I cannot dismiss the hundreds of conversations I have had in my ten years managing a supplement store. I have heard first-hand stories of customers relaying their experiences with negative stomach reactions to sucralose or stevia. 

It’s possible that the type of sweetener used, or the high level of sweetness (recall that most of these artificial sweeteners are hundreds of times sweeter than table sugar) can be contributing to nausea. 

Note: I mention in my article on Are Ready Made Protein Shakes Healthy that these sorts of drinks can contain a lot of artificial sweeteners, which could lead to stomach upset.

How To Fix

If you have tried the other fixes listed here and are still experiencing nausea, try a product that is sweetened differently. If your current product uses sucralose, try one that is stevia-based or vice-versa. 

Some companies, like Beyond Yourself, will use a blend of stevia and sucralose to try to mitigate the symptoms associated with taking too much of either.

If changing protein powders doesn’t help the problem, try a completely unflavoured protein powder. 

4. You’re Taking Too Much Protein at Once

Old conventional wisdom had us all believing that our bodies couldn’t absorb more than 25-30 grams of protein at one time. In recent years, that’s been proven untrue, but does that mean you should start double scooping your protein shakes? Not necessarily. 

The body is really good at self-regulating, especially where amino acid absorption is concerned. The majority of amino acids are digested in the small intestines, which can hold and store a lot of amino acids until the body needs them. 

However, some enzymes are needed in the stomach and small intestines to break down the protein into these amino acids. If too much protein is consumed in one sitting, the digestive system might not be able to keep up with the demand of enzymes required for digestion. 

Until the body catches up on enzyme production, you could be left with a feeling of indigestion or nausea. 

How To Fix

The current standard for protein intake for optimal muscle gain is 1.6g of protein per kg of body weight per day, distributed over four meals. This translates to consuming 0.4g of protein per kg of body weight per meal. 

For a 200lb individual, this translates to around 36g of protein per serving. 

To minimize the likelihood of too much protein causing nausea, find your ideal grams of protein per serving and stay at or below that level.

Remember that you are not obligated to use the exact scoop size of your product. If your protein offers 25g per scoop and your ideal serving size is 36g, you can do 1 ⅓ scoop to get you close to that amount. 

Note: If you’re getting a lot of your protein intake throughout the day from protein powders, check out my other articles on 3 protein shakes a day and 4 protein shakes a day

5. You’re Drinking Your Protein Shake Too Quickly

Drinking your protein shake too quickly could be contributing to your nausea. This isn’t reserved just for protein shakes; consuming too much of anything too quickly can cause gastric upset.

Chugging your drink too fast can result in you swallowing more air which can cause bloating and gassiness. 

If you drank a pre-workout and/or consumed water during your workout, you could already have a reasonably large volume of water sitting in your stomach. Slamming a protein shake quickly can rapidly add to that existing volume, resulting in nausea. 

How To Fix

Take your time. Sip on your protein shake over several minutes rather than chugging it in one go. 

As an added tip, make sure to mix your protein shake with around 6-8oz of water rather than filling your entire shaker cup to minimize the extra volume load in the stomach.

Related Article: Protein Shakes After Cardio: Pros, Cons, & Should You Do It?

6. You’re Drinking Your Protein Shake Too Close to Your Workout

As you work out, the body focuses on getting blood to your muscles and lungs and focuses less on digestion. Slamming your protein shake too close to your workout before the body is ready to digest it can lead to nausea and upset stomach. 

Old school wisdom had us believe that there was a very narrow post-workout window to consume protein to gain muscle. This resulted in people throwing back protein shakes as quickly as they could post-workout. 

The reality is, muscles are sensitized to protein intake for up to 24 hours post workout, so the anabolic window isn’t as narrow as we initially thought. Research is indicating that the most important thing is getting adequate protein throughout the day, regardless of timing. 

How To Fix

Have your protein shake approx 30 minutes after your workout. 

Take time to properly cool down, get changed, and then enjoy your shake. 

7. You Have a Lactose Intolerance You Didn’t Know About

Lactose intolerance is defined by the inability to digest the sugar that is naturally found in milk products (called lactose). This typically occurs when the small intestine does not produce the enzyme lactase which is required to break down lactose.

The side effects of lactose intolerance include gas, bloating, diarrhea, or nausea which can appear anywhere between 30 minutes and 2 hours after consuming lactose. 

It is estimated that approximately 30 million American adults have some degree of lactose intolerance. 

A less common problem is protein intolerance, affecting an estimated 1.9% of adults. There are a variety of physiological reasons why this might occur, but the bottom line is that the body is unable to digest or effectively break down amino acids. 

Common symptoms of protein intolerance include gas, bloating, abdominal pain, and diarrhea. 

It is also possible to be reactive to casein protein, specifically. Casein is a protein found in milk that gives it its white color, and it tends to be more problematic to digestion than whey and vegan proteins. 

How To Fix

The most definitive way to find out if you have a lactose or milk protein allergy will be to get a diagnostic test done by a doctor. 

In the meantime, however, there are some ways that you can experiment to find a protein formula that suits you. 

For suspected lactose sensitivity: Choose a whey isolate or whey hydrolysate that has 0g of sugar on the ingredient list. Since lactose is a milk sugar, a formula that has no sugar in it should be virtually lactose-free. 

For a suspected milk protein allergy: Choose a vegan or animal-based (beef, salmon, egg) protein powder. 

If you love your protein powder and are reluctant to change, you could consider adding a digestive enzyme supplement. 

A product like Allmax Digestive Enzymes includes protease (an enzyme to break down protein) and lactase, which might help you better digest your protein and eliminate gastrointestinal symptoms.

Choosing A Whey Protein That Doesn’t Make You Nauseous

1. Dymatize ISo100

One of my favorite whey proteins is Dymatize Iso100. It has been filtered to remove the excess lactose, offers around 85% protein per scoop, and tastes great. It boasts a 4.7/5 rating on Amazon, based on over 19,000 ratings with many mentioning its great taste and easy digestibility.

2. Vega Sport Protein

If you want to avoid whey protein altogether, Vega Sport Protein powder offers one of the highest overall grams of protein per scoop (30g) and sits at 68% protein per scoop. It’s rated at 4.5/5 on over 10,000 Amazon ratings and is certified safe for tested athletes and gluten-free.

What To Do If You Still Get Sick After Implementing These Tips

If you have tried finding a lactose-free or vegan formula, and adapting the timing of your protein intake, then it’s possible that a protein powder supplement simply isn’t the right avenue for you. 

Instead, try a food-based meal or protein supplement post workout. Some examples include

  • Tuna 
  • Hard boiled eggs
  • Greek yogurt or cottage cheese

If you still want the convenience of a grab-and-go snack, try a protein bar like Grenade Bars or Iron Vegan Bars.

Other Side Effects of Protein Powder

Frequently Asked Questions

How Common Is It For People To Get Sick After Drinking Whey Protein?

It is relatively common for people to get nauseous after drinking whey protein, because it can happen for a lot of reasons. It could be due to the protein itself (low quality, artificial sweeteners, added fiber, milk allergy) or due to how you’re drinking protein (too much, too fast, or too soon after a workout).

If I Get Nauseous After Drinking Whey Protein Does The Protein Go To Waste?

While getting nauseous can be irritating and uncomfortable, your protein hasn’t gone to waste if you get nauseous. As long as you do not throw up the protein, it will be digested and broken down into the amino acids necessary for recovery and muscle growth. 

Can Drinking Too Much Protein Make You Nauseous?

Yes, drinking too much protein can make you nauseous. Consuming too much protein in one serving (more than 50g), or drinking it too quickly or with too much water can all lead to nausea. Mix 20-40g of protein with 6-8oz of water, and sip on it over the course of several minutes to reduce the likelihood of nausea.

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About The Author

Jennifer Vibert
Jennifer Vibert

Jennifer Vibert is a Certified Strength and Conditioning Specialist, Nutrition Coach, and supplement store manager. She has a Bachelor of Kinesiology with a major in Fitness and Lifestyle and a minor in Psychology from the University of Regina. She is a Certified Nutrition Coach through Precision Nutrition, with a passion for helping clients learn the fundamentals of nutrition and supplementation in order to build healthy, sustainable habits.